The present invention relates to an electronic still camera capable of recording images of objects on a recording medium such as a magnetic disk.
In a conventional electronic still camera of a so-called single-lens reflex type as illustrated in FIG. 1, a lens 1 causes light from an object, not shown, to be incident on a pickup element 2. A quick return mirror 3 reflects the light from the lens 1 and causes it to be incident on a finder 5. A shift mechanism 4 drives the quick return mirror 3. A mirror 6 is fitted to the back side of the mirror 3 and capable of revolving, so that part of pickup luminous flux is caused to be incident on a photometric element 7.
While a release switch (not shown) is not held on, the quick return mirror 3 is located as shown by the solid line in FIG. 1. As the light passed through the lens 1 and is reflected from the quick return mirror 3 and caused to be incident on the finder 5 in the way stated above, the subject can be monitored via the finder 5, the quick return mirror 3 and the lens 1.
Moreover, the light passed through the quick return mirror 3, which is a half mirror, is reflected from the mirror 6 and caused to be incident on the photometric element 7. As a result, aperture value, shutter speed and the like can be computed from the output of the photometric element 7.
When the release switch is turned on, the shift mechanism 4 operates to move the quick return mirror 3 together with the mirror 6 upward (to the position indicated by the dashed (imaginary) line). Consequently, the light from the lens 1 is caused to be incident on the pickup element 2; thus the output of the pickup element 2 can be recorded on a recording medium such as a magnetic disk.
After this pickup and recording operation has been terminated, the quick return mirror 3 is returned back to the original position.
Since the quick return mirror 3 is thus disposed between the lens 1 and the pickup element 2 in the conventional electronic still camera of the so-called single-lens reflex type, the distance (back focal distance) between the back surface of the lens 1 and an image forming position (where the pickup element 2 has been disposed) has to be set large. In order to obtain a desired f-number with the large back focal distance, a large lens 1 will have to be used accordingly. Further, the quick return mirror 3 must be large in size. Although the back focal distance may be decreased to a certain extent by reducing the size of the quick return mirror 3, the amount of light incident to the finder 5 decreases, thus causing the brightness of the finder field to be reduced. Consequently, the size of the quick return mirror 3 cannot be reduced so much as desired.
In the conventional electronic still camera, the photometric element 7 has to be equipped besides (adjacent to) the pickup (photographing) element 2. Further, a TTL (through the taking lens) system is required in order to obtain an accurate exposure time. Still further, if the camera employs the quick return mirror system, additional mirror 6, as described above, is necessary for directing the light to the photometric element 7, which makes the mechanism more complex.
As above, it has been hardly possible to make a compact electronic still camera of the single-lens reflex type.